Could Extraterrestrial Pollution Be a Sign of Life in Space?

A novel approach to the search for intelligent (or not so intelligent) beings.

We like to think of Earth as a pretty special place in this universe. We’ve got water, we’ve got life, we’ve got human industry. Plus, we've got boatloads of industrial pollutants now contributing to our self-destruction.

But what if that last characteristic wasn't so unique? What if there were other planets outside our solar system also filling their atmospheres with chlorofluorocarbons (CFCs)? Could we find them by following their trail of pollution?

A new study suggests that, in the search for extraterrestrial intelligence, CFCs should be considered evidence of highly civilized life forms, much in the way that scientists have suggested looking for infrared radiation in the past. And soon we’ll have a means of sleuthing out possible exoplanetary pollutants: The researchers prove that the James Webb Space Telescope—the Hubble’s grand successor, expected to launch in 2018—should be capable of detecting at least two kinds of CFCs, under certain conditions.

“People have talked for years about looking for biosignatures such as oxygen on planets outside our solar system, because where there’s oxygen, there’s at least primitive life,” says Abraham Loeb, a renowned astrophysicist and an author of the study. “But with respect to intelligent life, to finding truly developed civilizations, that's where our research could lead.”

The conditions where the new telescope could detect CFCs are specific: It would have to be on an Earthlike planet circling a white dwarf star (which is essentially a dead sun). In that scenario, the starlight would be faint enough to not outshine compounds in the planet’s atmosphere. Finding pollutants on an Earthlike planet orbiting a Sunlike star would call for an even more specialized telescope, possibly one equipped with a gigantic, flower-shaped parasol—or a “star shade,” pictured below.

Think it seems silly to invest so much in hunting for ET? Loeb thinks that’s closed-minded. “We think we’re really special, that we’re the only thinking organisms out there,” he says. “Well, once upon a time, people were certain that the sun revolved around the Earth. There could be a second Copernican revolution if we discovered intelligent life.”

Or not-so intelligent life, if they’re strangling their planet they way we are.

About the Author

Laura Bliss is CityLab’s West Coast bureau chief. She also writes MapLab, a biweekly newsletter about maps (subscribe here). Her work has appeared in The New York Times, The Atlantic, Los Angeles magazine, and beyond.